1. Field of the Invention
The present invention relates to smoking articles such as cigarettes and to wrappers for such smoking articles which reduce ignition proclivity, i.e., the tendency to cause ignition of surfaces which come in contact with the lit cigarette. Reports have been made of fires attributed to burning cigarettes coming in contact with combustible materials. Such reports have generated interest in reducing the tendency of cigarettes to ignite surfaces and materials forming furniture, bedding, and the like upon contact. One obviously desirable attribute of cigarettes in this regard would be that they extinguish themselves if accidentally or carelessly dropped upon such combustible materials or surfaces. Since it is recognized by those skilled in the art that the wrapper strongly influences the behavior of a cigarette during smolder, modification of the wrapper construction to achieve these desired results would be highly beneficial. In particular, such a wrapper construction that does so without serious detrimental effects on desired smoking properties and characteristics would be especially advantageous. The present invention is directed to such wrapper constructions and improved smoking articles.
2. Description of the Prior Art
The subject of reducing the tendency of cigarettes to ignite upholstery, bedding, and the like has received much attention. Considerable effort has been directed to modification of cigarette papers to reduce to reduce fire hazards, including the development of non-burning wrappers for example as disclosed in U.S. Pat. No. 2,998,012 to Lamm dated Aug. 29, 1961, and design of wrappers having patterned rings or areas of non-burning materials for example as disclosed in U.S. Pat. No. 4,044,778 to Cohn dated Aug. 30, 1977.
It is also known, as in U.S. Pat. No. 4,321,377 to Cline, for example, to treat conventional wrappers with chemical adjuvants such as alkali metal citrates to control burn properties.
It is, moreover, known as described in copending and coassigned U.S. patent application Ser. No. 334,120 filed Dec. 24, 1981, now U.S. Pat. No. 4,461,311 dated July 24, 1984 to Mathews, DeLucia, and Mattina that the addition of extraordinary amounts of burn promotion additives to cigarette paper leads to a reduced emission of sidestream smoke. Cigarettes made with such papers normally would not have reduced ignition proclivity, however.
Additionally, copending and coassigned U.S. patent application Ser. No. 521,306 filed Aug. 8, 1983 refiled as Ser. No. 627,711 on July 11, 1984, describes wrappers for self-extinguishing cigarettes where the wrappers are treated in zones with elevated levels of burn promotion additives. Cigarettes made with these wrappers will not provide continuous free burn since they burn normally for a designed period of time and then reliably self-extinguish in air.
In summary, in spite of this extensive activity, it remains desired to produce a wrapper for cigarettes and the like that would result in the cigarette self-extinguishing when in contact with a substrate, including many composed of combustible materials, but which would otherwise perform as a conventional cigarette in terms of smoke delivery, puff count, free burn rate, and the like.